The present invention relates in general to apparatus for metering, mixing and dispensing materials and particularly to air powered and operated material dispensing devices.
Heretofore, it has been common to employ hand operated air powered dispenser devices or "guns" for selectively dispensing one-part sealant, adhesive or other material applications from disposable plastic cartridges having rear end closing movable plungers and forward end nozzle mounting apertures by application of air pressure or ram pressure on the cartridge plunger as in the prior U.S. Pat. No. 3,813,012. In that U.S. patent, a particular air control and valve means including flexible tubular conduits acted upon by a spring biased trigger actuator provides for application of air pressure to the cartridge plunger. However, the air powered sealant dispenser of U.S. Pat. No. 3,813,012 and other similar single cartridge dispenser devices are not suitable for metering, mixing and dispensing materials which must be stored in two parts, in separate cartridges, prior to use. By way of example, various rigid foam insulation materials, such as a plyether urethane foam comprises a two part, carbon dioxide low foam system which cures at room temperature to a rigid, closed cell, foamed insulation within a relatively few hours time. The two part components, however, may have a shelf life when stored in unopened disposable plastic cartridges at normal room temperatures of some 6 months time. It is therefore necessary to store the two part components separately, and then just prior to application meter the respective parts in desired proportions, mix the two parts together and then exude the mixture into a desired location. Other types of materials having separately stored base and accelerator components require similar handling preparatory to application.
Because of the permanent damage a mixed two part material may do to a dispensing apparatus after curing and setting of the material, time consuming and expensive clean up operations must be utilized with any device capable of metering and mixing such materials. Disposable storage and mixing cartridges have therefore been developed heretofore such as in U.S. Pat. Nos. 3,164,303; 3,153,531 and 3,144,966. The approach of these patents has been to provide a disposable cartridge having initially separate storage areas for two part material components with provision for initially mixing and then exuding the materials from the cartridge. From the nature of the approach, the capacity of such cartridges and the flexibility thereof has been limited. Various manual steps have also been required for initially mixing and then exuding the two part materials contained within the disposable cartridge assembly.